drm/msm/hdmi: don't take extra reference on PHY device

The of_find_device_by_node() already increments the device's usage
count, so there is no need to increment it again using get_device().
Drop this extra get_device().

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/499648/
Link: https://lore.kernel.org/r/20220826093927.851597-5-dmitry.baryshkov@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>